[libcamera-devel] [RFC 1/4] libcamera: camera_sensor: Cache rotationTransform_

[Laurent Pinchart]

Hi Jacopo,

Thank you for the patch.

On Tue, Jun 20, 2023 at 04:29:01PM +0200, Jacopo Mondi via libcamera-devel wrote:
> The rotationTransform_ depends on a V4L2 control whose value does not
> change for the whole lifetime of the camera.
> 
> Instead of re-calculating it everytime the camera is configured, cache
> it at properties initialization time.
> 
> Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> ---
>  include/libcamera/internal/camera_sensor.h |  1 +
>  src/libcamera/camera_sensor.cpp            | 54 +++++++++++++---------
>  2 files changed, 32 insertions(+), 23 deletions(-)
> 
> diff --git a/include/libcamera/internal/camera_sensor.h b/include/libcamera/internal/camera_sensor.h
> index 02c77ab037da..02b4b4d25e6d 100644
> --- a/include/libcamera/internal/camera_sensor.h
> +++ b/include/libcamera/internal/camera_sensor.h
> @@ -107,6 +107,7 @@ private:
>  	Rectangle activeArea_;
>  	const BayerFormat *bayerFormat_;
>  	bool supportFlips_;
> +	Transform rotationTransform_;
>  
>  	ControlList properties_;
>  
> diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp
> index f3a5aa37149f..a15a6c89c5c8 100644
> --- a/src/libcamera/camera_sensor.cpp
> +++ b/src/libcamera/camera_sensor.cpp
> @@ -461,18 +461,36 @@ int CameraSensor::initProperties()
>  
>  	const auto &rotationControl = controls.find(V4L2_CID_CAMERA_SENSOR_ROTATION);
>  	if (rotationControl != controls.end()) {
> +		propertyValue = rotationControl->second.def().get<int32_t>();
> +
>  		/*
> -		 * validateTransform() compensates for the mounting rotation.
> -		 * However, as a camera sensor can only compensate rotations
> -		 * by applying H/VFlips, only rotation of 180 degrees are
> -		 * automatically compensated. The other valid rotations (Rot90
> -		 * and Rot270) require transposition, which the camera sensor
> -		 * cannot perform, so leave them untouched.
> +		 * Cache the Transform associated with the camera mounting
> +		 * rotation for later use in validateTransform().
> +		 */
> +		bool success;
> +		rotationTransform_ = transformFromRotation(propertyValue, &success);
> +		if (!success) {
> +			LOG(CameraSensor, Warning)
> +				<< "Invalid rotation of " << propertyValue
> +				<< " degrees - ignoring";
> +			rotationTransform_ = Transform::Identity;
> +		}
> +
> +		/*
> +		 * Adjust property::Rotation as validateTransform() compensates
> +		 * for the mounting rotation. However, as a camera sensor can
> +		 * only compensate rotations by applying H/VFlips, only rotation
> +		 * of 180 degrees are automatically compensated. The other valid
> +		 * rotations (Rot90 and Rot270) require transposition, which the
> +		 * camera sensor cannot perform, so leave them untouched.
>  		 */
> -		propertyValue = rotationControl->second.def().get<int32_t>();
>  		if (propertyValue == 180 && supportFlips_)
>  			propertyValue = 0;
>  		properties_.set(properties::Rotation, propertyValue);
> +	} else {
> +		LOG(CameraSensor, Warning)
> +			<< "Rotation control not available, default to 0 degreees";

I think "degrees" has enough e's without having to add an extra one :-)
With this fixed,

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> +		rotationTransform_ = Transform::Identity;
>  	}
>  
>  	properties_.set(properties::PixelArraySize, pixelArraySize_);
> @@ -1038,21 +1056,11 @@ void CameraSensor::updateControlInfo()
>   */
>  Transform CameraSensor::validateTransform(Transform *transform) const
>  {
> -	/* Adjust the requested transform to compensate the sensor mounting rotation. */
> -	const ControlInfoMap &controls = subdev_->controls();
> -	int rotation = 0;
> -
> -	const auto &rotationControl = controls.find(V4L2_CID_CAMERA_SENSOR_ROTATION);
> -	if (rotationControl != controls.end())
> -		rotation = rotationControl->second.def().get<int32_t>();
> -
> -	bool success;
> -	Transform rotationTransform = transformFromRotation(rotation, &success);
> -	if (!success)
> -		LOG(CameraSensor, Warning) << "Invalid rotation of " << rotation
> -					   << " degrees - ignoring";
> -
> -	Transform combined = *transform * rotationTransform;
> +	/*
> +	 * Combine the requested transform to compensate the sensor mounting
> +	 * rotation.
> +	 */
> +	Transform combined = *transform * rotationTransform_;
>  
>  	/*
>  	 * We combine the platform and user transform, but must "adjust away"
> @@ -1083,7 +1091,7 @@ Transform CameraSensor::validateTransform(Transform *transform) const
>  		 * rise to this is the inverse of the rotation. (Recall that
>  		 * combined = transform * rotationTransform.)
>  		 */
> -		*transform = -rotationTransform;
> +		*transform = -rotationTransform_;
>  		combined = Transform::Identity;
>  	}
>  

-- 
Regards,

Laurent Pinchart